Bureau des Longitudes
The
Bureau des Longitudes is a
French scientific institution, founded by decree of
June 25 1795 and charged with the improvement of nautical
navigation,
standardisation of
time-keeping,
geodesy and astronomical observation. During the
19th century, it was responsible for
synchornizing clocks across the world. It was headed during this time by
François Arago and
Henri Poincaré. The Bureau now functions as an
academy and still meets monthly to discuss topics related to
astronomy.
The Bureau was founded by the
National Convention after it heard a report drawn up jointly by the Committee of Navy, the Committee of Finances and the Committee of State education.
Henri Grégoire had brought to the attention of the National Convention France's failing maritime power and the naval mastery of
England, proposing that improvements in navigation would lay the foundations for a renaissance in naval strength. As a result, the Bureau was established with authority over the
Paris Observatory and all other astronomical establishments throughout France. The Bureau was charged with taking control of the seas away from the
English and improving accuracy when tracking the longitudes of ships through astronomical observations and reliable clocks.
The ten original members of its founding board were:
*Geometers:
**
Joseph-Louis Lagrange;
**
Pierre-Simon Laplace;
*
Astronomers:
**
Joseph Jérôme Lefrançais de Lalande;
**
Pierre Méchain;
**
Jean Baptiste Joseph Delambre;
**
Dominique, comte de Cassini;
*
Jean-Charles de Borda, who carried out work related to the
mechanics of
fluids and precusor of
Carnot because of his insights on
thermodynamics;
*
Jean-Nicolas Buache,
geographer;
*
Louis Antoine de Bougainville, celebrated
navigator; and
*
Noël Simon Caroché,
manufacturer of
telescopes.
By a decree of
January 30 1854, the Bureau's mission was extended to embrace geodesy, time standardisation and astronomical measurements. This decree granted independence to the
Paris Observatory, separating it from the Bureau, and focused the efforts of the Bureau on
time and
astronomy. The Bureau was successful at setting a universal time in Paris via air pulses sent through
pneumatic tubes. It later worked to synchronize time across the
French colonial empire by determining the length of time for a signal to make a round trip to and from a French
colony.
The French Bureau of Longitude established a commission in the year
1897 to extend the to the measurement of
time. They planned to abolish the antiquated division of the day into
hours,
minutes, and
seconds, and replace it by a division into tenths, thousandths, and hundred thousandths of a
day. This was a revival of a
dream that was in the minds of the creators of the metric system at the time of the
French Revolution a hundred years earlier. Some members of the Bureau of Longitude commission introduced a
compromise proposal, retaining the old-fashioned hour as the basic unit of time and dividing it into hundredths and ten thousandths. Poincaré served as secretary of the commission and took its work very seriously, writing several of its reports. He was a fervent believer in a
universal metric system. But he lost the battle. The rest of the world outside France gave no support to the commission's proposals, and the French government was not prepared to go it alone. After three years of hard work, the commission was dissolved in 1900.
Since
1970, the board has been constituted with 13 members, 3 nominated by the
Académie des Sciences. Since
1998, practical work has been carried out by the
Institut de mécanique céleste et de calcul des éphémérides.
Connaissance des temps, astronomical
ephemerides, published annually since
1679;
Annuaire du Bureau des longitude,
almanac and
calendar for public and civil use, published annually since
1795;
Éphémérides nautiques, (from
1889) for marine navigation;
Éphémérides aéronautiques, (from
1938) for civil and military aerial navigation.
*
Bureau Des Longitudes (French)
*
Galison, Peter Louis (2003).
Einstein's Clocks, Poincaré's Maps: Empires of Time. Hodder & Stoughton. ISBN 034079447X.
*Dyson, Freeman J. (November 6, 2003).
Clockwork Science.
The New York Review of Books 50 (17)
*
The Office of Longitudes (French)
*
Official website (in French)
